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The New Horizons probe helped establish that the Kuiper belt is much larger than previously thought

The belt of icy debris circling the outer solar system may be much larger than we thought. Data from the New Horizons probe, which floats serenely through the Kuiper Belt, shows unexpectedly high numbers of particles where the dust should have died down, suggesting that the belt extends much further from the Sun than previously thought.

"New Horizons makes the first direct measurements of interplanetary dust far beyond Neptune and Pluto, so every observation has the potential to lead to a discovery," says physicist Alex Doner of the University of Colorado Boulder.

"That we may have discovered an extended Kuiper Belt - with a whole new population of objects colliding and producing more dust - provides another clue to the mysteries of the solar system's outermost regions."

The Kuiper Belt is characterized by a high density of rocky and icy objects (icy because they are very far from the Sun and very cold). It's filled with large rocks and dwarf planets, as well as a number of objects that we can't see because they're relatively small, and it's very dark. But dust can tell us a lot about what's going on there.

The Kuiper Belt was already considered huge. It begins in the orbit of Neptune, about 30 astronomical units from the Sun, and extends outward to an unknown exact distance. However, until now it was believed that the inner main region ends at about 50 AU.

New Horizons is a NASA probe launched to explore the outer solar system. In 2015, it visited Pluto, which orbits the Sun at an average distance of 39 AU, and continued on its way. In January 2019, it flew past a strange object called Arrokoth, which orbits the Sun at an average distance of 44.6 AU.

Since then, between distances of 45 and 55 AU. from the Sun, New Horizons continued to collect data, diligently transmitting it to Earth. As a result, the Venetia Burney Student Dust Counter (SDC) detects much more dust than scientists expected at this distance.

High dust densities mean that either additional dust is generated there, or solar radiation forces are suddenly pushing dust from denser regions into that space.

The most likely source of additional dust would be interactions between large objects - such as collisions. This means that there must be enough ice rocks there that they collide with each other with relative frequency.

More recent telescope observations have suggested that the inner core region of the Kuiper Belt may extend out to 80 AU, meaning the discovery is consistent with hints that the Kuiper Belt may be larger than thought.

At the time of writing, New Horizons is located at a distance of more than 58 AU. from the sun. It is now on its second long-duration mission, performing beyond initial expectations and continuing to send data home. Scientists hope that it will last until at least 100 AU, and if lucky, then to the very edge of the Solar system, beyond 120 AU.

The New Horizons probe helped establish that the Kuiper belt is much larger than previously thought